1. Field of the Invention
The present invention relates to a white light source, and more particularly, to a method of manufacturing a white light source having an excellent luminous efficacy.
2. Description of the Related Art
A representative white light source is a fluorescent lamp. The fluorescent lamp uses the emission of light by a fluorescent body due to a discharge effect. This fluorescent lamp has the drawback of low luminance. Moreover, it is difficult to miniaturize the fluorescent lamp and lower operating voltage in the fluorescent lamp. In addition, as use time lapses, the luminance of the fluorescent lamp decreases. Consequently, the stability and reliability of the fluorescent lamp are degraded, and the life span is short.
To solve the above problems, a feature of the present invention is to provide a white light source having an excellent electron emission efficiency in an applied electric field to thereby obtain a large emission current even at a low applied voltage, and having a very high density of electron emitters per unit area to thereby exhibit excellent luminance, and a fabrication method thereof.
In order to achieve the above feature, the present invention provides a white light source including a metal film used as a cathode, the metal film being formed on a lower substrate, a catalytic metal film formed on the metal film, carbon nanotubes for emission of electrons in an applied electric field, the carbon nanotubes being vertically aligned on the catalytic metal film, spacers mounted on the catalytic metal film, and a transparent upper substrate to which a transparent electrode to be used as an anode is attached, to which the transparent electrode a fluorescent body is attached, the transparent upper substrate being mounted on the spacers such that the fluorescent body faces the carbon nanotubes.
The catalytic metal film may be composed of isolated nano-sized catalytic metal particles, and the carbon nanotubes may be vertically grown from each of the catalytic metal particles by chemical vapor deposition. Here, the catalytic metal film may be formed of cobalt, nickel, iron, yttrium or an alloy of at least two of them, and the fluorescent body may be formed of (3Ca3(PO4)2CaFCl/Sb,Mn), generating a white luminescence, or a combination of Y2O3:Eu, CeMaA11O19:Tb and BaMg2Al16O7:Eu, to generate a white luminescence by combining different emission spectrums.
The white light source may further includes an insulation film pattern having openings selectively exposing the catalytic metal film. The carbon nanotubes are selectively located on the portions of the catalytic metal film exposed through the openings. The spacers may be mounted on the insulation film pattern.
The present invention also provides a method of fabricating a white light source. A metal film used as a cathode is formed on a lower substrate. A catalytic metal film is formed on the metal film. Carbon nanotubes for emission of electrons in an applied electric field are grown to be vertically aligned on the catalytic metal film. A spacer is mounted on the catalytic metal film. A transparent upper substrate having a transparent electrode having a fluorescent body is mounted on the spacer such that the fluorescent body faces the carbon nanotubes, and the transparent upper substrate is sealed with the lower substrate.
A reaction preventing film may also be formed using an insulating material to prevent reaction between the lower substrate and the metal film, before the step of forming the metal film. Here, the catalytic metal film is formed by depositing the catalytic metal film and etching the deposited catalytic metal film to separate the catalytic metal film into nano-sized catalytic metal particles. The carbon nanotubes are grown from each of the catalytic metal particles to be vertically aligned on the substrate by chemical vapor deposition.
For the catalytic metal film, cobalt, nickel, iron, yttrium or an alloy of at least two of them may be used. An insulation film pattern having openings selectively exposing the catalytic metal film may also be formed on the catalytic metal film. Here, the carbon nanotubes are selectively located on the portions of the catalytic metal film exposed through the openings, and the spacers may be mounted on the insulation film pattern.
The present invention can provide a white light source, which can be extremely miniaturized to be portable, and which has high efficiency and a power saving effect.